[volt-nuts] AC voltage "standards".

[acbern at gmx.de]

these instruments are painfull to use, complex measurement procedures and pretty unstable (if you want to use their ppm resolution). I spend hours and hours calibrating a set. lots of data available from standards labs.
what I would recommend is a ballantine 1605A. easy to use, very precise, well priced, broad frequency range but needs to be calibrated of course as well. you could go from one single calibrated thermal converter (e.g. 10V) and with e.g. a nanovoltmeter (34420A)  you could do a full 1605 ladder calibration. poor man's 792...





> Gesendet: Donnerstag, 09. April 2015 um 21:17 Uhr
> Von: "Chuck Harris" <cfharris at erols.com>
> An: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
> Betreff: Re: [volt-nuts] AC voltage "standards".
>
> Those are not references, but rather are AC thermal
> transfer standards.
> 
> The way they work is you apply an unknown AC voltage
> to it, and measure the DC voltage generated by
> its thermocouple.  Then you remove the AC voltage,
> and apply a DC voltage that gives the same thermocouple
> voltage.  Usually, you apply the DC voltage with both
> polarities, and average the two readings... which helps
> to null out any thermocouple errors.
> 
> To successfully use an AC thermal transfer standard it
> helps to have the controller instrument that goes along
> with it.
> 
> Fluke makes as nice setup, as did HP.
> 
> At their best, they are twidgety, and quite sensitive to
> ambient temperature variations, physical orientation,
> air currents....  Apply too much voltage, and like the
> light bulbs that they resemble, they go poof!
> 
> I don't think any metrologist has ever been truly happy
> with the AC thermo transfer standard.
> 
> -Chuck Harris